One form of construction of interior walls, partitions, soffits or the like, involves the use of structural framing covered on at least one side by sheets of plasterboard, or dry wall material, butted edge-to-edge. The plasterboard is generally manufactured in standard size sheets, such as four feet by eight feet, or four feet by ten feet, and may be 1/2, 5/8, or 3/4 of an inch in thickness. The plasterboard sheets are cut in-the-field to size; and tape means and a plaster-composition may then be used over the butted joints of the plasterboard sheets, and sanded down to define a smooth finished surface.
For walls, partitions or soffits having two flat sheets of plasterboard meeting one another at an exterior corner, a metal "corner bead" piece is used to cover the exposed edges of the plasterboard sheets, or structural corner as such will hereinafter be termed in this disclosure, and to define a solid and true corner edge. The corner bead piece is somewhat L-shaped, having a pair of generally flat legs connected to one another across a slightly rounded exterior corner or bead. The legs are angled relative to one another at just slightly less than 90 degrees, to allow that the piece can be set tightly in place over the exterior structural corner, and have the exposed corner bead set straight and true. Nails may then be driven through holes in the legs of the corner bead piece, through the underlying plasterboard, and into the underlying framing, to secure the corner bead piece in place at, and over, the exterior structural corner.
The tape means and plaster-composition may then also be used over the corner bead piece up the the corner itself, again being sanded down to define smooth finished corner surfaces.
The corner bead pieces would be originally fabricated to a standard length, typically eight (8) or ten (10) feet in length. Consequently, any structural corner extended a distance in excess of this would require that several corner bead pieces be butted together, end-to-end, along the corner. To give a good overall appearance, the adjacent beads must line up along a reasonably straight and smooth edge. This may require that the installer be quite close to the anticipated joint, to visually and/or physically by touch, set the finished bead line. This final adjustment would be accomplished by proper shifting about of the corner bead piece, again by grasping the piece with a free hand.
For rapid high-output installation of the corner bead pieces, a crimping tool may be used, instead of nails. One form of crimping tool has an elongated frame comprising two faces angled at right angles across an interior corner. The corner of the tool is adapted to be positioned over the corner bead piece when the latter is itself in place over the exposed edges of the meeting plasterboard sheets, at the exterior structural corner. Crimping pins are pivoted to the frame, one relative to each face, and each pin has an end that in one position is recessed behind the face, but the pin can be shifted in another position whereat pin end projects forwardly of the tool face. A striker is mounted on the frame to move relative to, toward or away from, the tool faces; and the striker is connected by linkage to the crimping pins. The striker is adapted to be hit with a mallet or the like to shift the crimping pins, rapidly and with sufficient force, against the underlying corner bead piece, operable to crimp part of the corner bead piece into the plasterboard so as to secure the corner bead piece over the exterior structural corner.
In using the tool, the mallet is first tapped against the frame part of the tool to firm the corner bead piece against the underlying exterior structural corner, and is then smacked harder against the striker to produce the crimps in the corner bead piece. The tool can then be relaxed off of the corner bead piece, initially while yet holding the corner bead piece with the mallet hand, and moved axially along the corner bead piece some 6-10 inches, or the like, to set up again and make other crimps. After several crimps have been made, the corner bead piece will be sufficently held in place that one need not further hold the corner bead piece when shifting the tool between making additional crimps.
One major disadvantage of the discussed crimping tool is the difficulty in having one person simultaneously handle the separate corner bead piece, the tool, and the mallet, in lining up the corner bead piece properly before initially setting it in place. This task can be particularly slow, and unnerving, when stretching out to reach an overhead corner, and/or when working off a ladder or scaffold with any threatening factor of height or degree of sway and instability.
Thus, one might temporarily hold the mallet in one's tool-carrying belt loop or pinched between one's legs, or may set the mallet down on some adjacent ledge or the like. The tool and the corner bead piece may then be held and manipulated by two free hands; first to position the corner bead piece over the exterior structural corner with the one end lined up properly to butt against the wall, floor or ceiling extended transverse to the structural corner or edge-to-edge with the adjacent secured corner piece, and then to position the tool over the corner bead piece. The corner bead piece is now trapped and held in place by the tool itself. Consequently, the hand originally holding the corner bead piece is now free and can be used to pick up the mallet, and to hit the tool to set and secure the corner bead piece.